Electron discharge apparatus



'HARTMAN 2,469,964 I 3 Sheets-Sheet 1 I I I I F- I EL INVENT'O/E P.L.HARTMAN 9mm 6. M

ATTORNEY May 10, 1949 ELECTRON DISCHARGE APPARATUS Filed May 3, 1941 P. L. HARTMAN ELECTRON DISCHARGE APPARATUS May 10, 1949.

Filed May 3, 1941 3 Sheets-Sheet 2 m T m l- P.

ATTORNEY y P. L. HARTMAN ELECTRON DISCHARGE APPARATUS 3 Sheets-Sheet 3 Filed May 3; 1941 A T TOR/VE V Patented May 10, 1949 ED STAT ES ELEGTRON DISCHARGEv APPARATUS ApplicationMay 3, 1941, Serial Not-391,689

11 Claims; (Cl. 2'5027.5)

This invention relates to ultra-high frequency electron discharge apparatus and more particularly to-ele'ctron beam discharge devices operable as amplifiers or oscillators at frequencies corresponding to wave-lengths of a-few centimeters.

In onekn'own type" of electron discharge apparatusfcramplifying or generating ultra-high frequency' electrical impulses, an electron beam is subjected to a cyclically varying field inthe direction of projection of the beam" whereby locity variations in thebeam are produced The beam then traverses a regon, commonly referred to as the drift space, whereby a bunching of the fast and" s'1'0W"m0Vingje1ectrons in the beam occursatsome distance from the region of velocity variation. The bunches of electrons'flow. in proximity to a suitable" outputfelement and"- deliver power thereto by induction.

In such apparatus, the field resulting in the velocity variations is usually produce-d by impressing' a. suitable. potential between a pairv of electrode membershaving alignedrestrictedpassageways at opposite ends of: agapthrough which the beam flows. Thepenetrationof. the field into the gap is limited so that the effect ofthe applied potential and the field due thereto upon the electrons in the gapislikewi'selimited. In addition, the field in the gap is non-uniform so that different electrons in. the beam: acquire difierent percentages of= velocity variation and as a result sharp bunching of the electrons is. not realized. Also, of necessity the beam is of small cross-sectional dimensions so that the power capacity of the apparatus is limited and space charge effects, particularly in the drif tnspa'ce, are fairlyl-arge so that nonz-uniformitiesin 1 operating characteriistics may result.

One general object of the invention is to enable the generation and" amplification of ultrahigh frequency electric signals.

More particularly; obj cots-' of this" invention are to improve the operating chara'cteristics of electron beam" dis-charge devices of the type wherein an electron-beam is subjected" to afield for cyclically varying" the velo'cityof"theelectrons in the beam, to obtain substantially uniform variation of all of the electrons in the beam, to increase the efficiency of the source producing the variations, to reduce space charge effects in such. de- Vices andto increase the: powercapacity ofsuch devices;

In one illustrative embodiment-of this invention, ultra-high frequency electron discharge apparatus comprises a; pair of parallel deflector plates defining an input gap, an output element,

such as a cavity resonator having" a ga -therein,

2" and. an electron gun for projectinga concentrated-stream into theinput gap;

In accordance with one feature of this'invention, the input and output gaps are located at diametrically oppositepoints offa circle' and means are provided for'xproducing a magnetic field between the gaps and'normalto" the direction. of projection of the. electron beam into'the input gap so that'the-electronsare directed alon arcuate trajectories" substantially along the'circle in flowing fromtheinput' gap to-th'e output gap. An electric 'fi'eld" isproduced between the deflector plates so that'a velocityvariation; normal to the initial electron" velocity; is eifected and the ele'ctronitrajectoriesbetween the input and: output gaps. are therebyvaried according 1y; The magnetic field and the field produced between the deflector plates are correlated so that a bunching of the electrons is effected and the electron bunches traversetheoutput gap in the proper phase" relation tov deliver energy to the output elem ent.

The apparatus maybeutilized-as an-amplifier, in which case the signal to be amplified is impressed betweenthe deflector plates. It may be utilized also to generate-ultra-high' frequency oscillations, in which case the deflector plates are associated with the output' element in su'chmanner that a portion of the energy de1ivered t0-the output element is fed back tothe input gap to maintain oscillations.

In a specific embodiment; the electron beam is velocity'varied in the direction of' its projection into the input gap; prior to its projection into the input gap; and a constant field is maintained between the deflector plates whereby the'velocity variations are converted into density variations at the output gap by the trajectory'variation effect upon theel'ectron streamat the inputgap.

The invention and t-heaforenoted and other features thereof will'b'e understood more clearly and fully from the following detaileddescription with reference to the accompanying drawing in which? 7 Fig. 1' is inpart a perspectiveview of' an electron discharge device constructed in accordance with this invention" and in art a circuit diagram illustrating one mannerof operating the device, a portion of the enclosing vessel of the device being broken awayto' show details of'constructi-on moreclearly Fig. 2-" is a diagrammatic View illustrating the relationship of the'el'ectrodes and output el'em'ent in the device shown in Fig. 1iandiindicatingjtypical electron.trajectoriesinithisdevice;

Figs; 3 and '4 are" diagrammatic" viewsillustrating the form and arrangement of the electrodes in modifications of the embodiment of this invention shown in Fig. 1;

Fig. 5 is a diagrammatic view illustrating an ultra-high frequency oscillation generator constructed in accordance with this invention;

Fig. 6 is a perspective view of an electron discharge device embodying the construction illustrated diagrammatically in Fig. 5;

Fig. 7 is another diagrammatic view illustrating another embodiment of this invention suitable for push-pull operation; and

Fig. 3 is still another diagrammatic view illustrating another embodiment of this invention suitable for converting velocity variations in an electron beam into density variations.

Referring now to the drawing, the electron discharge device illustrated in Fig. 1 comprises an evacuated enclosing vessel having a substantially semicircular portion I0, for example of non-magnetic metallic material, and cylindrical end portions II and I2, of insulating material such as glass. Mounted within the end portion II of the enclosing vessel is an electron gun, designated generally as G, and including a cathode I3 and a plurality of coaxial electrodes I4, I5 and I6 in axial alignment with the cathode I3 for concentrating the electrons emanating therefrom into an accelerated beam which is projected between a pair of parallel deflector plates I'I positioned on opposite sides of and equally spaced from the longitudinal axis of the electron gun. The deflector plates I! are connected to the conductors of a tunable coaxial input line 28, the outer conductor being grounded, whereby a high frequency potential may be impressed between the deflector plates.

Adjacent the end portion I2 of the enclosing vessel is a, cavity resonator I8 having therein a gap I9 substantially coplanar with the mid-point of the space between the deflector plates I 7. Energy may be taken from the cavity I8 through a coupling loop projecting into the cavity and connected to the wall thereof as shown. Mounted enclosing vessel of the device for producing in the semicircular portion thereof a uniform magnetic field parallel to the deflector plates i1 and the gap I9 and normal to the longitudinal axis of the electron gun.

During operation of the device, the electrodes I4, I5 and I6 of the electron gun are maintained at successively higher positive potentials with respect to the cathode I3 by a suitable source such as a battery 23, and the collector electrode 2i is maintained at an intermediate potential, as by the battery.

The electrons emanating from the cathode I3 are concentrated into a beam which is projected into the magnetic field and normal to the lines of the field. At their point of injection into the field and between the deflector plates H the electrons in the beam have substantially the same velocity and, when the deflector plates are at the same potential. are following parallel paths at these plates. Thus, as indicated in Fig. 2, in the absence of a potential difference between the plates H, the electrons are traveling normal to the plane X--X and normal to the magnetic field at a point 0 between the plates I7, the magnetic field being normal to the plane of the drawing.

4 Under the influence of the magnetic field, the electrons are directed along a semicircular path So and at substantially degrees from the point 0 across the gap I9 in the cavity resonator I8, traveling with their initial velocity.

If an alternating potential is impressed between the deflector plates H, the electron stream will be deflected accordingly and the electrons will then follow arcuate paths of the same radius, longer or shorter than the path So, in flowing to the gap I9, two illustrative paths being indicated in Fig. 2 by the lines S1 and S2. The effect of the deflecting potential is to vary the length of the trajectory of the electrons between the deflector plates I1 and the gap I9 periodically with time, the length being increased during onehalf cycle of deflecting potential and decreased during the other half cycle. Thus, referring to Fig. 2, during one-half cycle of the alternating potential applied between the deflector plates H, the electrons at the point 0 will be deflected toward the left and follow paths, such as the path S2, longer than the path So in flowing to the gap 59; during the other half cycle of deflecting potential, the electrons at the point 0 will be deflected toward the right in the figure and follow a path, such as the path S1, shorter than the path So in flowing to the gap I9. These trajectory variations may be used to produce periodic bunching of the electrons emanating from the electron gun, at the gap i9 whereby the cavity resonator will be energized and high frequency power may be taken therefrom. This will be understood from the following considerations.

Consider two electrons leaving the region 0 with the same velocity v, and at times apart, where T is the period of the deflecting potential applied between the plates I1, and following paths S1 and S2 respectively. The times required for these two electrons to reach the gap I9 will be, then,

respectively, and if the two electrons are to be bunched at the gap I9, i. e., pass through the gap at the same time,

The length of the path taken by an electron deflected at the time t can be shown to be where St is the length of the path, m and e are the mass and charge of the electron, H is the magnetic field and 01: is the angle of deflection at the time t. The time it, required for an electron traversing the path St in flowing from between the deflector plates I'! to the gap I9 is given by the relation m i T l- 1) If the extreme deflections are :0 coming onehalf cycle apart, the difference btween the two time flights may be expressed by the relation From Equations 1 and 4, then, it will be apparent that in order that bunching of the electrons leavingf'thwpoiht .eiiatltiznes oneeha-lfx cyclmaparii be effected} thes'fellowiugi'relationz mu'st-v hevsat isfiedt:

4t '11? th ir Inasmuch: as; asl'w-ill be'lapparent, the; relatiom is; necessarily satisfied;..tlie; radius 7 r of. the; path traversed by the. electrons; is;

WHIP

it being understood that the radius of ther'sev' eral' paths; su'cl'ras' St; St and: Si is the same, the" efi'ect of the""deflecting' potential being" to shift the center of curvature" of the -electron paths without altering the radius;

Hence; it will be-seen that by properly" corre latingjtlie -deflection" angle the magneticfleld H 'and'theperiod- T of' the deflecting potential impressed betweem plates 1T; electrons leaving the region between r the" plates-= l 1 one halii cycle apart willarrive at andtraverse tlie e'apl9-=in phase: Of" course; allother electrons leaving this region at other'times durin'gthis :-half="cyc1e will tend totraverse tl'ie"-- larr 19 in phase with one-another-and the two electrons leavihg1on'ehalf cycle apart. Stated-in another way; when the parametersenoted? are: ccrrelate'd ih accordance with Equatibn'i 5'}? the'e'lectrons leaving the region between the deflector plates M during anWhalfiycle 'of deflecting-potential arebunclied as: they pa'ss -theoutputgap 192* Hence, the (literat -current beam projected" betweenthe d e fle'ctor plates I 1? is converted int'o'a periodieally pulsing b'eaxn traversing the gap l 'g 'so that-the resonator l8 is energized! Inasmuch as but little power" need be expended in deflecting the b'eamprojected between the p1a teS-'l 1 and the beam current' may-be larga'it will be appreciated that ari ar'milifi'e'ati'o'rl of a signal' impressed aicro's's tile deflector plates I'T may he realized;-

It' will ibe liiiliefstbod} of course; thellj tfie spam mg of? tli seawater: 'pl'atesf M and the gap l-e shdul'd be related so that: the electromabeam velbcityz andi the magnetip helm-employed: iii-zany particular case, the radius r as -giv'em by the Equation 6, is such that the electron stream:prot J'e'ctedi betweeni the: plates H? and trajectbry variedbwthe alternating:- field'therehetweemwill passtthroughlthe": gap ISL- Aitenthe electrons traverse- -the= gap- IQ they are r. collected-'1 bythev collector electrode 2 ,2 which m'ay bemaintained'zat a poten-tial lbwer th'an that ofithe dectrodesi: lfi' arid l 6 of 'the e1'eetlt0n' orderitozconserveidirect" cur-rent: energy;'.zthe eleo' trons ldeingre'tarded before collectien Inasmuch as the beam traverses 'tlie 'varying elcflfidfleldTbEilWBelfithdeflectonpl'a'tes'; I the=p otentiai: l impressed: 'lietweem the'se 'plaltes behiehiy; effective upomth'ei electmm'streamamlta high zde'greeofimodulationl willithusliemrodiiced. Furthermore, the .field'the'tween the deflector plates is uniformz smthatialllof tlie e1ectronsq'a'asfs mg:therebetweensyatiany particularsinstant; suffer essentially "the: same force inornial'i to: thein projected :directiom and: thus acquire: substantially the same't'raieetory"variation whereby 'al liig l-l de gr'i oft-blanching: at tiled-gap: IS-Eislattained antiahigh, transconduotanoe llS' realizedi Also: inasmuichi.as'ctheeaverageivcross section of the beam in flowing from the region of the deflector plates to the ganwds relativeli l'ar'ge, space charge 64 eiicts im the-beam? will: be small; Finally; it'ewill be; appreciated ixthah as large currene beam: may belemployedi so that imultral-high frequency dee vicesl'constructedz in: accordance with. this 'inveni tilmylarge power" outputs'am'ay beiohtained.

Although: in: the embodiment; OI. theinvention illustrated r in: Figs. 1. and: 22 and described above; ther electronsgun i'simounted with itsrslongitudinal axls:--norm'al to the diameter: of: the traj ectoryx on which the deflector:- plates:- I 1: and: the: gap f9 lie; iti rmayr he mounted in"; other" positions: two-not which are illustrated. in Figs; 3 andi 4. Ih'srtlie construction illustratedinaFig: 3-,.the' electronaguri includestthe-cathode: I'3a and curved axially symmetricallelectrodesa I l'at i521: anal. lea, immersed-1m the ma'gnetie field-i and constructed and arranged so that-the axis: offthen gun: lies-along aware: of the same circleion whichthegap I9 and tnegap between the deflector plates 1 1. lie):

lnzthei'construetion showni in'iE'lg 43- the gun: is positioned outside of thezma'gnetie -field andithe electron stream: is projectedinto" the field at a velocity much: higher than: that to: which its velocity: isl reduoed just before its entrance'into -th'e gapihetween the deflector plates :l i.

The invention may be utilized also te generate ultra-high frequency oscillations; an: illustrative embodiment thereof suitable for thismurpose being: illustrated invFigs; 5 and Si As shown in t-liesef figurea the' resonantitcavity lBa -is associated witlithe defleetorrplates iii; the plates','.-as ind-io'ateuiinrxFigz 6; beingimoun'ted atone'en'd of the gap; new in: the V cavity I812: and energy being cleliver-edito theacavity byrthe traiectoryivariedelem tron strea'm; at the. otll'enen'd of thegap- I Saz- As thea'cavityis excited.by thestl'eam, some energy will be 'fed back vt'o the deflector plates so thatisus t'ainecI-z oscillations Will'- be produced;' Therequisite magnetic field" is. produced by the 1 magnet niusliown inphantom iii-Fig. 6;

In the embodiment of 'th'e invention illustrated inlEig; 7;.which .is a mo-dificatl'on of that illustrated in' Figs: 5 and 6; the deflector plates 11 are mounted at: the center *of the gap [9a, twocolopposite ends of the gap Wel and--two"electron guns:- Gi and: are'provided for projecting two eleetr'on beanie between the deflector 'pla'tes-= 1 I l afi'dl in: opposite directions: Each stream trajectory var-led atithe' deflector plates N and en'- e'ng y 'isl'de'livered to the resonant c'avity at both eud's oilthe gap tSa whereby oscillations-Memo"- duced and. maintained, the operat ion-being pushpull characteh as will be apparent.

Iii -the embodimentsillust'rat'eddnFigsz 5', (land 7; itiwill be understood that a magnetiefield' hormallto'sthe direction of projection ofthe' electron streamxorstreams' isem'ployed, asdescribe'dheretoforaintconne'ctiom with Figs: 1 and Also?" it will be noted that in the embbdiinents illustrated irml'iess 5; (i ands-7g theelectrongun is outside of theioavity "andt: hence; outside 1 of the: highire"- quemzyfieldi In the embodiment of the invention illustrated inzEig; l, 8;. thevelectronibeam proj (acted by the gun traverses-the: gapi'; in a cavity "resonator-4U", passes-betweenxthe deflectorpl'ates l'J 'andiMlbWs aniarcuatecpath in-the=magnetie--fielii ihl-fiowing t-ozrthez'gap "ma-in: the -resoriantlcavity 1-8. A cons'tanttdii ectfxourrent;field-sis produoed betWeen-the deflectolt'platesw i l; a'sa'b'y' a= batter-v 4 h semen-e meansysnot showm; are provided to:- energize the resonant cavitw-w whereby;-v in crossihg tlie gap ihszthismavitit, ti'le eleotron s'tream velb'eit'y varied;

aecaeoe The deflection given to any electron by the field between the plates I! as the electron passes between these plates is dependent upon the velocity of the electron as it enters this field. That is to say, an electron having a relatively small velocity when projected into this field will sufier a greater deflection than an electron projected into this field with a relatively higher velocity. Hence, when an electron stream, velocity varied by the action of the resonant cavity 40, is projected between the deflector plates H a trajectory variation of the beam occurs and, as will be understood from the description of the operation of the apparatus shown in Figs. 1 and 2, the electrons in the beam will be bunched as they pass through the output gap l9, so that the velocity variations produced at the gap in the cavity resonator 49 are converted into density variations effective to energize the resonant cavity [8. Energy may be taken from the cavity resonator 18 through the conductor 25..

Although specific embodiments of the invention have been shown and described, it will be understood that they are but illustrative and that various modifications may be made therein without departing from the scope and spirit of the invention as defined in the appended claims.

What is claimed is:

1. Electron discharge apparatus comprising an input element having spaced members defining an input gap, means for projecting a stream of electrons through said gap, means for directing the electrons in said stream along an arcuate path after the electrons leave said gap, an output element inductively energizable by said electron stream having an output gap positioned substantially 180 degrees from said input gap along said arcuate path, and means for producing a periodic grouping at said output gap of the electrons in said stream including means for impressing upon said electron stream while traversing the input gap a cyclically varying velocity component normal to the direction of projection of the electron stream into said input gap and substantially in the direction of a line connecting said input and output gaps.

2. Electron discharge apparatus in accordance with claim 1 wherein said first means includes an electron gun projecting a substantially univelocity electron stream into said gap and wherein said last means includes means for impressing a high frequency potential between the spaced members defining the input gap.

3. Electron discharge apparatus in accordance with claim 1 wherein said last means includes means for producing a constant direct current field between the members defining the input gap and includes also means for velocity varying the electron stream prior to the projection thereof into the input gap.

1. Electron discharge apparatus in accordance with claim 1 comprising means for conveying energy from said output element to said input p.

5. Electron discharge apparatus comprising means for producing a magnetic field, means for projecting an electron stream into said field substantially normal to the lines of force thereof whereby said stream is directed along an arcuate path, output means inductively energizable by said stream and having a gap positioned substantially 189 degrees along said path from the point of entrance of said stream into said magnetic field, and means for cyclically deflecting said stream adjacent said point and normal .to. the

8 lines of force of said field and in the direction of projection of said stream into said field.

6. Electron discharge apparatus comprising a cavity resonator having an elongated gap therein, a pair of deflector plates mounted at one region in said gap and energizable by said resonator, an electron gun for projecting a stream of electrons between said deflector plates, and means for producing a magnetic field normal to the direction of projection of said electron stream between said plates and of such intensity as to direct said stream along a semicircular path one end of which is located at a point in said gap and the other end of which is between said deflector plates.

7. Electron discharge apparatus comprising a cavity resonator having a gap therein, and means for energizing said resonator, said means including an electron gun for producing an electron stream at a region spaced from said gap and in a direction substantially parallel to the axis of said gap, means for producing a magnetic field having its lines of force substantially parallel to said gap and substantially normal to the initial direction of said electron stream, to direct said stream along an are having one end adjacent said gun and its other end at said gap, and means for deflecting said stream adjacent said one end of said arc and substantially normal to the lines of force of said field.

8. Electron discharge apparatus in accordance with claim I comprising means for feeding back energy from said cavity to said deflecting means.

9. Electron discharge apparatus comprising a pair of deflector plates defining an input gap, a pair of output elements equally spaced from and on opposite sides of said input gap, each of said elements being located at a region substantially degrees along an arcuate path from said input gap, a pair of electron guns for projecting two electron streams through said input gap in opposite directions, and means for producing a magnetic field in a region including said input gap and output elements, said field having its lines of force normal to the directions of projection of said streams into said input gap and being of such intensity to direct each of said streams along one of said arcuate paths and to the output element adjacent the corresponding path.

10. An electron discharge device comprising electrode means for producing an electron beam of constant velocity, means contiguous to the path of said beam for oscillating said beam transversely for varying the transit time of the electrons of the beam as a function of the transverse displacement of the beam and producing a density modulation, and means in the path of said beam for intercepting said beam at its point of maximum density.

- 11. An electron discharge device comprising electrode means for producing an electron beam of constant velocity and in an arcuate direction of constant radius, means contiguous to the path of said beam for oscillating said beam with a lateral component for varying the arcuate length of path of travel of the beam and thereby varying the transit time of the electrons of the beam as a function of the lateral displacement of the beam and producing a density modulation, and means in the path of said beam for intercepting said beam at its point of maximum density.

PAUL L. HAR'IMAN.

(References on following page) REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,138,928 Klemperer Dec. 6, 1938 2,197,338 Fritz Apr. 16, 1940 CTHER REFERENCES Journal of Applied Physics, vol. 10, No. 12, Dec. 1939, p. 868. 

